Is it physical or mental – or a combination of the two? And why are treatments for CFS hotly disputed? In an extract from her book Cure, Jo Marchant tells the story of Samantha Miller, one sufferer of the controversial condition

Paul Anderson wanted to die. He'd been ill for years and had tried to take his life three times. The next time, his wife Jill decided to respect his wishes. And she was charged with manslaughter. Hannah Booth meets her